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US Department of Energy National Science Bowl


Back to EurekAlert! A Service of the American Association for the Advancement of Science

 

Closer to the customer

ORNL helps bring reliable, energy-efficient cooling, heating, and power to commercial customers nationwide.



Power outage headlines appear in newspapers across the nation.

Without warning, the August 14, 2003, power blackout removed electricity for millions of people in the United States and Canada. The next day manufacturers still had no power, contributing to an estimated cost to the U.S. economy of $6 billion. Meanwhile, in Ontario, New York, Harbec Plastics, which machines complicated plastics parts, operated during the blackout without interruption, owing to an array of 25 Capstone microturbines. Fired by natural gas, each microturbine produces 30 kilowatts (kW) of electricity and virtually no pollutants. The array's waste heat is recovered and used both to heat water and air (in winter) and cool the building space in summer.

Typically, about two-thirds of the fuel energy used to generate electricity in central power stations is discarded as waste heat and then as losses incurred in power transmission and distribution. By the time the power reaches the point of use, total efficiency can drop to 30%. However, efficiency can be raised to more than 70% by locating each power source close to the customer and productively using the source's waste heat for heating, cooling, and controlling humidity in each appropriately sized commercial or institutional building. Since the 1990s the Department of Energy and the private sector have worked together to develop such distributed energy (DE) technologies, also called cooling, heating, and power (CHP) units and, more recently, integrated energy systems (IES).

DOE is seeking to demonstrate that IES units in operation throughout the United States can increase the nation's energy efficiency, reliability, and security, reduce dependence on imported oil, and simultaneously lower emissions of pollutants that threaten health and a stable climate. DOE's goals are to develop the next generation of clean, efficient, reliable, and affordable DE technologies, integrate these technologies into appropriately sized end-use sites, and capture waste heat, or thermal energy, to more than double energy efficiency for heating and cooling of buildings.

Ready for Prime Time

DOE asked ORNL to focus on three types of energy sources, or "prime movers," for IES units: industrial gas turbines, reciprocating engines, and microturbines. All of these sources can burn natural gas and produce two types of energy: electricity and waste heat. These sources would be integrated with a "thermally activated" technology, such as an absorption chiller for cooling, a desiccant wheel for dehumidification, or a steam generator or heat exchanger for heating water or air.



This microturbine in the ORNL Recuperator Testing Facility is used to test metal specimens to determine their suitability for high-temperature recuperators.

ORNL supported the development by UTC Power, a United Technologies Company, of the UTC PureComfort™ system, a reliable IES with ultra-low emissions that features a 112-ton absorption chiller powered by waste heat from four to six 60-kW microturbines. The double-effect chiller provides cooling and heating from the same unit, conserving space and simplifying design. In summer the chiller uses waste heat from the microturbine as the source of energy for driving the fluid that extracts heat from water to chill and provide air conditioning. The CHP technology has an efficiency of up to 80%.

ORNL researchers have teamed with industrial partners to figure out how to capture heat from each turbine or engine and transfer the heat to a thermally activated system to provide cooling, dehumidification, or heating. ORNL's Jim Sand has promoted the use of waste heat for dehumidification in schools and other buildings to improve air quality and prevent the growth of mold and other allergens. Waste heat from engines and turbines can be combined with a desiccant system to create a more comfortable environment where temperature and humidity are controlled independently. Air can be passed through a desiccant wheel, which absorbs the moisture and sends the resulting dry air into the building. The waste heat dries the desiccant wheel so that it can again pick up moisture from indoor air.

In 2001 DOE asked ORNL to solicit proposals from companies that manufacture engines, turbines, and heat exchangers, as well as from end users that can benefit from IES units. ORNL personnel served as technical project managers in cost-shared contracts between DOE and industry, which bore 43% of the cost. The ORNL project managers provided technical expertise to the industrial partners and helped identify the best ways to capture waste heat for making what the end user wanted, such as chilled water for air conditioning or heat for steam. By 2004 several partners had met the DOE goal of combining individually optimized products on-site.

One project at a hospital and strategic command center at Fort Bragg Army Base in North Carolina included a gas turbine, absorption chiller, steam generator, and Honeywell control system that constantly provides power, heating, and cooling. A second project was a gas turbine that provides both electricity and chilled water for air conditioning to the tenants of an Austin, Texas, industrial park. A third was a project in New York where a skid-mounted UTC PureComfort 240 system was installed on the roof of an A&P Supermarket. The system supplies electricity and chilled water year-round for the supermarket's refrigeration cases. Waste heat is also used to heat the supermarket in the winter months.

The DOE goal for 2010 is that each manufacturer would produce a single optimized IES package because each integrated or modular IES package will be more cost effective, require little on-site engineering, and offer a higher overall energy efficiency. By 2010 DOE hopes to show that single optimized IES packages can meet targets of a 32% reduction in energy usage and a 46% reduction in carbon dioxide emissions. ORNL is contributing to this effort by helping with integration, size reduction, and packaging of CHP technologies to improve energy efficiency.

ORNL researchers are also working with industrial partners to oversee the design, development, installation, and operation of IES units in larger market sectors such as hotels, supermarkets, hospitals and medical centers, movie theaters, and high schools and colleges. In 2004 the ORNL researchers—Randy Hudson, Jan Berry, Jim Sand, and Therese Stovall—began monitoring and collecting data on the operation of the newly installed IES units throughout the country.

Research Payoffs

Patti Garland, an ORNL engineer and CHP program manager, has been a principal investigator for experiments at DOE's Integrated Energy Systems Test Center at the University of Maryland. "We integrated off-the-shelf equipment into an IES unit at the university's Chesapeake Building," she says. "This building, which is occupied by more than 150 people, has four miles of cables and more than 190 data points from which we measure real-time operating performance of the test equipment. We conducted performance testing on the IES there, collected data, made some mistakes, and, based on the lessons we learned, provided recommendations to industry on how to improve designs of IES equipment. A valuable recommendation was to install an airtight damper to isolate the microturbine exhaust from the absorption chiller when the chiller is not operating."



A city's night-time energy use.

According to Bob DeVault, the highly instrumented CHP laboratory at ORNL where he works was the first lab to test both a microturbine and heat exchanger simultaneously and as a system over the whole range of thermal conditions. Neither the microturbine vendor nor the heat exchanger manufacturer is set up to conduct the types of tests that ORNL can do.

The ORNL research should help industry and DOE meet two goals by 2010. The first goal is to double the amount of CHP capacity in the United States, bringing it to 92 gigawatts of installed capacity. The second goal is to build and install packaged systems with an energy efficiency of at least 70% and a payback of 4 years or less—that is, the amount of money saved by reduced demand for energy would cover each system's additional capital cost in no more than 4 years.

According to Dave Stinton, a manager of ORNL's Distributed Energy Program, ORNL researchers have been developing advanced materials to increase the efficiency of engines and turbines. They have been evaluating the longevity of continuous fiber-reinforced ceramic composites used in combustor liners and the oxide coatings that protect these liners against oxidation in industrial gas turbines built by Solar Turbines, Inc.



ORNL researchers will evaluate integrated energy system projects at Wal-Mart stores.

"We also conduct research on natural-gas-burning reciprocating engines in collaboration with Caterpillar, Cummins, and Waukesha," Stinton says. "Reciprocating engines are more efficient than gas turbines and microturbines but have higher emissions of nitrogen oxides (NOx). Our challenge has been to reduce emissions from the engine by an order of magnitude and increase the efficiency to 50%."

"We have developed a NOx trap that reduces the NOx emissions from lean-burn engines to 0.1 g/hp/hr, meeting the goal of the program for 2010, " says Tim Theiss, manager of ORNL's Advanced Reciprocating Engine Systems Program.

ORNL researchers are working in partnership with industry to extend the life of spark plugs for natural gas-fired reciprocating engines to 8000 hours, delaying the need for maintenance from several months to one year. Laboratory staff who collaborate with Federal Mogul, makers of Champion spark plugs, believe that use of alternative materials will result in a cheaper, more durable, corrosion-resistant spark plug.

ORNL is now working with Capstone, UTC, and General Electric with a goal of raising the efficiency of microturbines from 27% to 40%. "The ability to operate a microturbine at higher and higher temperatures will lead to higher efficiencies, but this operating level will be possible only with the right materials," says ORNL's Edgar Lara-Curzio. "We have been screening and evaluating materials for a microturbine component that is responsible for one half of the microturbine's efficiency. We selected an innovative approach for screening and evaluating candidate materials that should enable us to identify the right materials for the hot section and recuperator of an advanced microturbine."

"What we are trying to do in the short term is use better metals to get the hot section up to an intermediate temperature range," Stinton says. "Capstone's beta version of a metal microturbine demonstrates 34% efficiency.

"We are looking at silicon nitride for a microturbine's rotor, the hottest part of this machine. Use of a ceramic rotor would raise the turbine inlet temperature by several hundred degrees Celsius, boosting the microturbine's efficiency to nearly 40%."

As a result of the latest solicitation, ORNL is involved in IES projects not only with hotel and supermarket chains but also with Wal-Mart stores and McDonald's restaurants. These projects offer potential for reliable, as well as efficient, energy sources. In 2003 a new IES protected the critical circuits of the Hilton Garden Inn in Chesterton, Indiana, when a violent thunderstorm caused a four-hour electrical outage in the area. The hotel's guests enjoyed normal operations including a hot lunch during the outage.

"These partnerships are exciting because they should enable a new technology to be replicated nationwide," Stinton says. "IES units already are cost effective in many parts of the United States. We are very enthusiastic about the potential of this technology as one solution to America's energy challenge."

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